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  Electricity Practice Exam Study Guide Version

Electricity & Fields Exam

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
 

 1. 

If you walk into a region of space and suddenly feel a force, the space is said to contain a
a.
charged object.
b.
force field.
c.
large charge.
d.
black hole.
e.
heavy object.
 

 2. 

An electric field has
a.
direction.
b.
magnitude.
c.
Both A and B
 

 3. 

The direction of electric field lines shows the
a.
direction of the force on a test positive charge.
b.
size of the field.
c.
strength of the field.
d.
all of the above
 

 4. 

If two negative charges are held close together and then released, the charges will
a.
accelerate toward each other.
b.
accelerate away from each other.
c.
not move.
d.
move at a constant speed away from each other.
 

 5. 

A volt is a unit of
a.
charge.
b.
electric potential.
c.
energy.
d.
work.
e.
current.
 

 6. 

In order for there to be a flow of charge from one place to another, there must be a
a.
conductor, such as a wire, connecting the two places.
b.
potential difference between the two places.
c.
Both A and B above
 

 7. 

In solid conductors, electric current is the flow of
a.
positive and negative charges.
b.
electrons.
c.
negative ions.
d.
protons.
e.
none of the above
 

 8. 

An ampere is a
a.
unit of resistance.
b.
unit of current.
c.
type of charge.
d.
voltage.
e.
current.
 

 9. 

An example of a voltage source is
a.
an electrical outlet.
b.
a generator.
c.
a car battery.
d.
rubbing a balloon on your head.
e.
all of the above
 

 10. 

Electrical resistance is measured in
a.
volts.
b.
joules.
c.
watts.
d.
amperes.
e.
none of the above
 

 11. 

When we say an appliance uses up electricity, we really are saying that
a.
electrons are taken out of the circuit and put somewhere else.
b.
electron kinetic energy is changed into heat and other forms of energy.
c.
the main power supply voltage is lowered.
d.
current disappears.
 

 12. 

Electric power is defined as
a.
current times voltage.
b.
current divided by voltage.
c.
current times resistance.
d.
resistance times voltage.
e.
voltage divided by current.
 

 13. 

When an 8-V battery is connected to a resistor, 2 A of current flows in the resistor. What is the resistor's value?
a.
2 ohms
b.
4 ohms
c.
8 ohms
d.
16 ohms
e.
more than 16 ohms
 

 14. 

The current through a 5-ohm resistor connected to a 150-V power supply is
a.
1A.
b.
10 A.
c.
30 A.
d.
150 A.
e.
none of the above
 

 15. 

A 15-ohm resistor has a 5-A current in it. What is the voltage across the resistor?
a.
5 V
b.
15 V
c.
20 V
d.
25 V
e.
more than 25 V
 

 16. 

What is the resistance of a toaster that uses 5 A of current when connected to a 120-volt power source?
a.
5 ohms
b.
24 ohms
c.
120 ohms
d.
600 ohms
e.
none of the above
 

 17. 

When connected to a 110-volt power supply, how much current is in a light bulb that has a resistance of 220 ohms?
a.
0.5 A
b.
2.0 A
c.
110 A
d.
220 A
e.
24,200 A
 

 18. 

How much power is used by a 12.0-V car battery that draws 0.5 A of current?
a.
0.5 W
b.
6 W
c.
12 W
d.
24 W
e.
30 W
 

 19. 

When resistors are put in series next to each other, their overall resistance is
a.
the same as the resistance of one of the resistors.
b.
larger than the resistance of any individual resistor.
c.
smaller than the resistance of any of the resistors.
 

 20. 

In a simple parallel circuit
a.
current through each branch is always the same.
b.
voltage across each branch is always the same.
c.
the value of each resistor is the same.
d.
none of the above
 

 21. 

Fuses and circuit breakers are used to
a.
protect us.
b.
prevent overloading.
c.
keep wires from getting overheated.
d.
break the circuit when too much current is being used.
e.
all of the above
 

 22. 

The total resistance of a 10-ohm resistor and a 7-ohm resistor in series is
a.
2 ohms.
b.
3 ohms.
c.
7 ohms.
d.
17 ohms.
e.
70 ohms.
 

 23. 

Surrounding every moving electron is
a.
an electric field.
b.
a magnetic field.
c.
both A and B
d.
none of the above
 

 24. 

If the north pole of one magnet is brought near the south pole of another magnet, the poles will
a.
repel each other.
b.
attract each other.
c.
not interact with each other at all.
 

 25. 

If you put a small compass in a magnetic field, the compass will
a.
line up in a direction parallel to the magnetic field lines.
b.
swing randomly.
c.
line up in a direction perpendicular to the magnetic field lines.
d.
seek electrical charge concentrations.
 

 26. 

Magnetic field strength is
a.
strongest close to a magnet.
b.
constant everywhere around a magnet.
c.
strongest far from a magnet.
 

 27. 

Magnetic fields are produced by
a.
moving particles of Earth.
b.
charges at rest.
c.
moving particles.
d.
moving charged particles.
e.
none of the above
 

 28. 

Loops of wire in a motor rotate because a
a.
battery effectively pushes a loop around in the field.
b.
current exerts a force on the loop, causing it to rotate.
c.
magnetic field exerts forces on moving electrons in the loop.
d.
magnet attracts stationary electrons in the wire.
e.
none of the above
 

 29. 

Electric current can best be induced in a wire by
a.
stretching the wire.
b.
moving a magnet back and forth near the wire.
c.
setting the wire near a magnet.
d.
none of the above
 

 30. 

The phenomenon of inducing voltage by changing the magnetic field around a conductor is called
a.
electromagnetic induction.
b.
generated voltage.
c.
Faraday's fartaday.
d.
electromagnetic radiation.
 

 31. 

A device that transforms electrical energy to mechanical energy is a
a.
generator.
b.
motor. 
c.
magnet.
d.
none of the above
 

 32. 

If a magnet is pushed into a coil, voltage is induced across the coil. If the same magnet is pushed into a coil with a greater speed
a.
a larger voltage is induced.
b.
a smaller voltage is induced.
c.
the same voltage is induced.
 

 33. 

An electric motor and an electric generator are
a.
entirely different devices.
b.
very similar devices.
 

 34. 

Electromagnetic waves travel at a speed
a.
approximately equal to the speed of light.
b.
much greater than the speed of light.
c.
much less than the speed of light.
 

True/False
Indicate whether the sentence or statement is true or false.
 

 35. 

When a charge is placed in a region of space where there is an electric field, the charge will experience a force.
 

 36. 

The energy a charge possesses by virtue of its location is called electrical potential energy.
 

 37. 

Charge will move in a conductor when there is a difference in potential between the ends of the conductor.
 

 38. 

Charge flows from low potential to high potential.
 

 39. 

The unit of electric current is the ampere.
 

 40. 

A resistor is something placed in a circuit that totally blocks the flow of electrons.
 

 41. 

When charge moves in a circuit, it normally heats part of the circuit.
 

 42. 

In a parallel circuit, current in each branch is the same.
 

 43. 

Magnetic poles are similar to electric charges in that they both can repel and attract one another.
 

 44. 

Because magnetism is slightly different from electrostatics, magnetic fields do not exist.
 

 45. 

A magnetic field is produced by the motion of charged particles.
 

 46. 

There is a magnetic field around a current-carrying wire.
 

 47. 

Faraday's law says that the induced voltage in a coil is proportional to the product of the number of loops and the rate at which the magnetic field changes within those loops.
 

 48. 

Underlying the operation of an electric motor is a current-carrying wire that is rotated when in a magnetic field.
 

 49. 

An electric field is induced in any region of space where a magnetic field is changing with time.
 

Essay
 

 50. 

What is a parallel circuit? How do voltages, currents, and resistances add in a parallel circuit? Give an example.
 

 51. 

What is a motor? Explain its operation.
 

Problem
 

 52. 

A 30-V potential difference is applied across a series combination of an 8.0-ohm resistor and a 3.0-ohm resistor. What is the current in the 8.0-ohm resistor?
 

 53. 

A 60-V potential difference is applied across a parallel combination of a 10-ohm and a 20-ohm resistor. What is the current in the 10-ohm resistor?
 



 
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